Method for the production of high precision glass stopcocks



11, 1953 M. MANES EIAL 2,643,179

METHOD FOR THE PRODUCTION OF HIGH PRECISION GLASS STOPCOCKS Filed Jan. 10, 1952 Fig.

INVENTORS Milton Manes Lawrence J.E. Hofer ber'r D. Hinkel BY ATTORNEY Patented Aug. 11, 1953 METHOD FOR THE PRODUCTION OF HIGH PRECISION GLASS STOPOOCKS Milton Manes, Lawrence J. E. Hofer, and Robert D. Hinkel, Pittsburgh, Pa.

Application January 10, 1952, Serial No. 265,911

(Granted under Title 35, U. S. Code (1952),

see. 266) 2 Claims.

The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention is concerned with an improved method for the production of high precision glass stopcocks and with the improved article pro duced thereby.

In many laboratory and industrial uses of glass stopcocks it is of great importance that the complementary barrel and plug members of the stopcock fit together with a high degree of precision. This is of particular importance, for example, in the handling of gases where a pressure differential is employed across the stopcock. In such applications it is often necessary that there be no leakage across the stopcock whatsoever after weeks or months of service and after the stopcock has been subjected to a large number of turns previously.

It is quite difficult by the usual methods of measurement to detect the imperfections that, in a stopcock which is apparently ground and lapped with a high degree of precision, will lead to leakage under exacting conditions of service. One practical test, however, is to properly lubricate the mating surfaces of the barrel and plug and then to turn the plug in the barrel a number of times while observing the occurrence of interruptions in the grease film which are usually visible as streaks. When a stopcock is in service,

these streaks or channels in the grease film form passages through which gases or liquids may leak. A high precision stopcock can be subjected to many (from 50 to 100) turns when properly lubricated without the occurrence of any streaks Or other interruptions in the grease film.

According to prior methods for the manufacture of glass stopcocks, first, the required number of ports are pulled or blown in the barrel or female member of the stopcock and the side arms are attached at the points where these ports have been formed. The interior surface of the barrel or female member is then ground to the tolerances required for proper mating with male or plug member. After the plug member is likewise ground to the required tolerances, the mate between the barrel and plug is usually further improved by lapping the two members together. Lapping together of the barrel and plug is usually a hand operation in which the craftsman turns the plug within the barrel, while supplying an appropriate lapping compound between the mating surfaces of the barrel and plug respectively, until a precision fit has been obtained.

One can sometimes find a highly skilled craftsman who, employing these prior art methods, can produce a stopcock which will not fail under exacting conditions of use, but it has generally not been possible for even a highly skilled craftsman to produce stopcocks of consistently high quality. This inconsistency in quality has often led to unfortunate results, since it is sometimes diflicult or impossible to detect a good stopcock from a bad one except under actual conditions of use. Failure of a single stopcock in service may spoil a long and difficult experiment causing the loss of a large amount of time and effort. It is an object of the present invention to overcome the disadvantages inherent in prior methods for the manufacture of glass stopcocks and to provide a method which consistently results in the production of high precision stopcocks and which at the same time requires no greater degree of skill and craftsmanship than prior methods.

It is a further object of the invention to provide a method for the manufacture of high precision glass stopcocks which, when properly lubricated, can be subjected to a large number of turns without any streaking or other type of interruption of the lubricating film between the mating surfaces of the stopcock.

It is a still further object of the invention to provide a high precision glass stopcock having complementary barrel and plug members made in accordance with the method herein described.

These and other objects of the invention will become apparent from a consideration of the de--v scription Which follows and of the accompanying drawings in which the various figures are semidiagrammatic illustrations of the steps involved in one method of carrying out the invention. The method of the invention for achieving the foregoing objects involves a particularsebeen formed) and then forming the necessary ports as a last step following the completion of the grinding and/or lapping operations by a method, such as drilling, which will not cause deformation of the ground surfaces. According t prior methods this sequence is reversed, the necessary ports being formed in the barrel or plug (or in both) before the grinding or lapping operations are undertaken.

For a better understanding of the invention, reference is now made to the accompanying drawings which illustrate the steps involved in one particular method for carrying out the invention in the manufacture of a relatively simple stopcock of the so-called solid-plug type.

Referring now to Figure 1, reference numeral l indicates the barrel or female member of the stopcock. The barrel may be formed by any convenient method so long as the mating surfaces 2 are left unbroken. At this stage, the mating surfaces 2 are unground and correspond only roughly to the configuration necessary for proper mating with the complementary plug member.

The next step in the operation is the fusing of the necessary side arms to the barrel or female member without breaking the mating surfaces 2 thereof. This is done by fusing short side arms to the outer surfaces of the barrel while causing as little demoration as possible of the inner surfaces. Figure 2 illustrates the barrel at this stage, with a pair of short side arms 3 attached to the opposite sides thereof. The reference numeral 4 refers to the point of attachment of the side arm 3 to the outer surfaces of the barrel. It will be noted that the mating surfaces 2 of the barrel are unbroken. According to prior methods, at this stage a pair of ports would have already been formed in the barrel at the base of the sidearms causing discontinuities in the mating surfaces 2.

The next operation involves the separate grinding of the mating surfaces of the barrel to the proper configuration for mating with the plug or male member. This operation is shown schematically in Figure 3, wherein the numeral 5 refers to a grinding mandrel having an abrasive coated tip 6.

Next, the male or plug member is likewise separately ground to the proper size and taper for mating with the barrel. This operation is illustrated in Figure 4 wherein the numeral 1 refers to the plug member having a handle portion 8. It will be noted that the mating surfaces 9 of the plug are continuous and unbroken. An abrasive coated die 10, held securely in a chuck II, keyed to a shaft [2 is employed for grinding the surface 9 to the desired configuration. It is clear of course that the separate grinding of the barrel and plug may be conducted in any desired manner, for example, with the use of loose, instead of a fixed abrasive, or in the case of the grinding of the plug, with the use of a centerless grinder instead of a grinding mandrel.

After the mating surfaces of the barrel and plug members have been separately ground, the barrel and plug are then lapped together to insure a more perfect mating thereof. This operation is illustrated in Figure 5. A suitable lapping compound is supplied between the mating surfaces 2 of the barrel and the mating surfaces 9 of the plug and the lapping operation conducted in the manner well known in the art with a combination twisting and thrusting motion of the plug within the barrel accompanied by the intermittent seating and unseating of the plug.

When, according to the judgment of the crafts man performing the operation, the lapping together of the barrel and plug is complete, the necessary passages in the wall of the barrel are formed preferably by drilling. This operation is shown in Figure 6 of the drawing. By means of the diamond tipped bit I3, a passage is drilled at the base of each of the short side arms 3. Preferably, the plug member is inserted into the barrel during the drilling operation to back up the wall thereof at the point Where the passage is being drilled to prevent chipping when the drill breaks the inner surface of the barrel well. The use of the plug for backing up the inner wall of the barrel during the operation of drilling ports in the barrel has the further advantage that the location of the corresponding ports in the plug can be marked with perfect accuracy merely by allowing the drill to penetrate slightly the surface of the plug after breaking through the inner barrel wall. Since all the grinding and lapping operations are, at this point, complete, there consequently will be no subsequent displacement of the ports relative to one another and the ports will be substantially in perfect alignment in the finished product. After the ports are formed in the barrel walls, tubing of any desired length may be fused onto the short side arms 3, care being taken to avoid heating the barrel to any substantial extent.

The final operation, namely the drilling of the necessary port in the plug member is illustrated in Figure '7. Preferably, the passage is drilled toward the center from opposite ends to minimize chipping of the mating surfaces. If necessary, the opposite ends of the port may be reamed out slightly to remove any irregularities introduced into the mating surfaces of the plug member by the drilling operation.

The major improvements which result from operation in accordance with the method of the invention are achieved during the operation of lapping together the barrel and plug members following the separate grinding thereof. It has been found particularly important to conduct this operation while the mating surfaces of the barrel and plug are still unbroken. However, even in the manufacture of a so-called standard taper stopcock wherein the operation of lapping together the barrel and plug members is omitted, some improvement is also obtained by forming the necessary ports in the barrel and plug only when the grinding operations are complete.

It will be understood of course, that the particular method described above and shown in the drawings is merely illustrative, and that this method may be modified as required to suit the particular type of stopcock being manufactured. For example, any number of side arms in any desired position may be attached to the barrel so long as the inner mating surfaces of the barrel remain unbroken until all the grinding and lapping operations are completed. If desired, the required number of side arms may be formed integral with the barrel by a single molding operation, and the communicating ports formed by drilling after the mating surfaces of the barrel have been properly ground and lapped. Similarly, any number of passages may be formed in the plug member at any desired angle. Likewise, a hollow or semihollow plug may be employed which may be vacuum seated or otherwise. In the case of a hollow plug, the usual practice is to seal a piece of open glass tubing between the opposite walls of the tubing forming the plug.

Operating according to the invention however, instead of an open glass tubing, a solid glass rod may be sealed across the opposite walls of the hollow plug and after the mating surfaces of the plug have been ground and lapped to the desired finish, a port may be formed through the plug by drilling through the glass rod. In this manner, the mating surfaces of the plug may be preserved continuous and unbroken during the grinding and/or lapping operations.

"Stopcocks made in accordance with the method of the invention, particularly those in which the process is carried to the step of lapping together the barrel and plug members, will give good service under the most exacting conditions of use. They have a marked ability to withstand a large number of turns without the formation of any streaks or discontinuities in the lubricant between the mating surfaces. Under equivalent service conditions, stopcocks made in accordance with the invention may be lubricated with a lighter grease than stopcocks made according to prior methods. For example, even under conditions of service where a pressure differential is employed across the stopcock, a light grease such as Apiezon grease L, or other suitable greases of low thixotropy may be employed without danger of leakage across the stopcock. The possibility of using lighter greases is a distinct advantage since, with the lighter greases there is a lessened tendency to form streaks or other discontinuities in the grease film. Under severe service conditions, stopcocks made according to prior methods generally require a rather heavy lubricant having a greater tendency to streak.

It is not usually possible to distinguish the stopcocks made in accordance with the method of the invention from those made by prior methods employing ordinary measuring tools or methods of observation. However, it has been found that when the mating surfaces of a stopcock are examined by sighting along the ground surfaces at a glancing angle in a plane generally parallel to the axis thereof, while observing the reflection of a straight line, distinct differences can be seen between stopcocks made in accordance with the invention and those made according to prior methods. The glancing angle of observation tends to make the surface more reflecting and to magnify surface distortion in the same way as the observation at a glancing angle of a reflection on a window glass pane tends to magnify the surface distortions. On such an examination, the surfaces of a stopcock made in accordance with prior methods usually show relatively sharp circumferential ridges and/or troughs, these markings being particularly noticeable at or in the vicinity of the ports. Stopcocks made in accordance With the invention on the other hand, are consistently characterized by the absence of these sharp circumferential ridges and troughs, any deviations in the ground surfaces being of a gently rolling character with no special markings at or in the vicinity of the ports. These sharp ridges and troughs are particularly apparent in stopcocks made according to prior methods when the barrel and plug members have been thoroughly lapped together. It is probable that the absence of these sharp deviations in the stopcocks made according to the invention is responsible for the improvements which are obtained.

,Although the utility of the invention does not depend on any theory concerning the reason for the improvements obtained, it is entirely possible that in prior methods the sharp ridges and troughs (which are observable only when the stopcock is examined as described above) are caused by the collection of loose abrasive at the open ports during the grinding and lapping operations. This theory would appear to explain the persistent occurrence of these sharp irregularities in the vicinity of the ports, and also to explain the fact that these irregularities become much more pronounced during the lapping together of the barrel and plug, since in this operation there is generally more loose abrasive available to collect at the open ports.

The term stopcock, as used in the specification and claims, is intended to include any device having mating ground surfaces with communicating ports formed in the mating surfaces in such manner that the ports are opened and closed by relative rotation of the mating surfaces.

It is to be understood that the above description, together with the specific examples and embodiments described, is intended merely to illustrate the invention, and that the invention is not to be limited thereto, nor in any Way restricted except by the scope of the appended claims.

We claim:

1. A method for the manufacture of high precision glass stopcocks having complementary barrel and plug members comprising the steps, in order, of forming the barrel and plug members thereof with unbroken mating surfaces, fusing side arms to the outer surfaces of said barrel without breaking the inner mating surfaces thereof, separately grinding the mating surfaces of said barrel and plug members while said mating surfaces are still unbroken, and then forming the necessary ports in said barrel and plug members respectively.

2. A method for the manufacture of high precision glass stopcocks having complementary barrel and plug members comprising the steps, in order, of forming the barrel and plug members thereof with unbroken mating surfaces, fusing side arms to the outer surfaces of said barrel without breaking the inner mating surfaces thereof, separately grinding the mating surfaces of said barrel and plug members while said mating surfaces are unbroken, lapping together said barrel and plug members with said mating surfaces still unbroken, and then forming the necessary ports in said barrel and plug members respectively.

MILTON MANES. LAWRENCE J. E. HOFER. ROBERT D. HINKEL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 914,244 Conradson Mar. 2, 1909 2,387,013 Fuller Oct. 16, 1945 2,427,849 Garwood Sept. 23, 1947 2,465,388 Monack et a1 Mar. 29, 1949 2,589,985 Borneman Mar. 18, 1952 

